Generally, passages for supplying compressed air to various pneumatically operated components used in various factories and atomic plants, for example, are usually provided with filter devices for removing water and oil contained in the compressed air, for the purpose of protecting the pneumatic components or improving the performance of those components.
One type of such a filter device for compressed air is disclosed in JP-A-5-200217, which is constructed to include two kinds of filter means. Namely, this filter device has first filter means having a suitable first packing accommodated in a sleeve, and second filter means having a suitable second packing accommodated in another sleeve. The first and second filter means are disposed parallel to each other. At one of axially opposite ends of the first and second filter means, there is disposed a manifold which includes an inlet passage portion and an outlet passage portion. The inlet passage portion has an inlet passage formed therein, through which the compressed air is introduced into the filter device. The outlet passage portion has an outlet passage formed therein, through which the compressed air is fed out from the filter device. The inlet and outlet passages communicate with the first and second filter means, respectively. At the other of axially opposite ends of the first and second filter means, there is disposed an enclosed trap chamber having a suitable volume, such that each of the first and second filter means communicates with the trap chamber. The thus arranged first and second filter means, the trap chamber and the manifold are assembled together and fixed to each other by a plurality of bolts which extend through the manifold and which are screwed in the trap chamber. According to this arrangement, the compressed air entering the inlet passage of the manifold is fed into the outlet passage of the manifold through the first filter means, the trap chamber, and the second filter means, whereby an air passage for the compressed air is formed through the filter device.
In the filter device constructed as described above, usually, the first packing of the first filter means is a roll of a wire mesh fabric formed by weaving or knitting stainless steel fibers or other metallic materials, so that vapor and/or liquid particles like water and oil contained in the compressed air are condensed or coalesced as the compressed air passes through the first filter means, while the second packing of the second filter means is a wound fabric mesh formed by weaving or knitting cotton fibers or other materials, so that the liquid particles contained in the compressed air are absorbed or vaporized as the compressed air passes through the second filter means.
Thus, in the filter device disclosed in the above-indicated publication, the vapor and/or liquid particles are condensed or coalesced as the compressed air is introduced into the trap chamber through the inlet passage of the manifold and the first filter means, so that the vapor and/or liquid particles are separated from the compressed air. Further, the compressed air from which the vapor and/or liquid particles have been thus separated is introduced into the second filter means through the trap chamber, so that the amount of the liquid particles remaining in the compressed air is minimized.
The first and second packings constituting the first and second filter means, respectively, are required to be replaced with clean ones when the packings get clogged with dust and/or grease. The replacement requires the following operations.
First, the plurality of bolts serving to connect the first and second filter means, the manifold and the trap chamber into an integral assembly are all removed, and the assembly is disassembled into the four parts. Secondly, the clogged first and second packings which are accommodated in the first and second sleeves, respectively, are replaced with clean ones. The first and second filter means, the trap chamber and the manifold are then reassembled together and fixed to each other, as described before, by screwing the plurality of bolts in the respective positions.
That is, in the conventional filter device disclosed in the above-identified publication, each time the first and second packings of the first and second filter means are replaced, the device has to be disassembled into the parts before the replacement, and the parts have to be reassembled into the device after the replacement.
The filter device is advantageously used in various factories, atomic plants and medical field owing to its high filtering performance. However, the filter device requires the above-described operations for replacing the first and second packings, which operations are cumbersome and time-consuming, as described above. There is still a room for improvement in this filter device.
The present inventor disclosed a filter device for compressed air in JP-A-9-10533 having a construction which solves the problem with the above-described filter device. The disclosed filter device includes first filter means having a first packing accommodated in a first sleeve, second filter means having a second packing accommodated in a second sleeve, an inlet passage portion defining an inlet passage which connects an exterior of the filter device and the first sleeve to introduce the compressed air from the exterior into the first filter means, a guide passage portion defining a guide passage which connects the first sleeve and the second sleeve to guide the compressed air from the first filter means into the second filter means, and an outlet passage portion defining an outlet passage which connects the second sleeve and the exterior to feed the compressed air out of the second filter means to the exterior. The first and second sleeves, the inlet passage portion, the guide passage portion and the outlet passage portion are formed of a synthetic resin, integrally with each other, so as to constitute a body of the filter device. The body is provided with access openings through which the first and second packings are removed from the filter device. To each of the access openings, a closure member is removably attached so as to fluid-tightly close the access openings.
This filter device for compressed air is constructed such that all the parts cooperating to form a fluid passage in the filter device are formed of a synthetic resin, integrally with each other so as to constitute the body of the filter device, and the body is provided with the access openings through which the first and second packings are removed. Further, the closure member is removably attached to each of the access openings so as to fluid-tightly close the access openings. According to this filter device, therefore, for replacing the clogged first and second packings, it is not necessary to carry out time-consuming operations such as disassembling of the filter device into the component parts and reassembling of the parts into the device. In this filter device, the clogged first and second packings can be replaced by new ones, by simply removing the caps from the respective access openings and re-attaching the caps to the respective access openings. Thus, the replacement of the first and second packings can be made more easily and quickly than in the conventional device.
However, as a result of further study made by the present inventor, this filter device proved to have the following problem. Upon the replacement of the clogged first and second packings in this filter device, the clogged packings are removed by a suitable tool formed of a wire or other material, since it is very difficult for the operator to pick the packings out of the respective sleeves, directly with the fingers. That is, the tool is put into the first and second sleeves through the respective access openings after removing the closure members from the access openings, so as to take out the clogged first and second packings. Thus, this filter device requires the tool for the replacement of the first and second packings and a certain amount of cumbersome work for taking out the clogged first and second packings through the access openings from which the closure members have been removed, although the device is constructed such that the closure members can be removed from the access openings without using a tool.